1. Technical Field
The present invention generally relates to a light emitting element and fabricating method thereof and more particularly to a light emitting diode (LED) and fabrication method thereof.
2. Description of the Related Art
Recently, since luminescence efficiency of LEDs has been constantly upgraded, application of fluorescent lamps and/or incandescent bulbs is gradually replaced with LEDs in some fields, such as scanning light source which requires high speed response, back or front light source of a liquid crystal display (LCD), car dashboard illumination, traffic signs and general illumination devices. Compared with the traditional bulbs, LED has absolute advantages. For example, an LED is physically compact, long lasting, low voltage/current driven, durable, mercury free (pollution free) and with high emissivity (power saving) etc.
FIG. 1 is a schematic cross-sectional view of the conventional light emitting diode. Referring to FIG. 1, light emitting diode 100 is composed of a substrate 110, an N-type semiconductor layer 120, an electrode 122, a light emitting layer 130, a P-type semiconductor layer 140 and an electrode 142. The N-type semiconductor layer 120, the light emitting layer 130, the P-type semiconductor layer 140 and the electrode 142 are sequentially disposed on the substrate 110. Furthermore, there is only a portion of the N-type semiconductor layer 120 covered by the light emitting layer 130 and the electrode 122 is disposed on the portion of the N-type semiconductor layer 120 which is uncovered by the light emitting layer 130.
Referring to FIG. 1 again, voltage difference between the N-type semiconductor layer 120 and the P-type semiconductor layer 140 is generated by applying voltages to the electrode 122 and the electrode 142 from external circuit. Then, the electrons provided by the N-type semiconductor layer 120 and the holes provided by the P-type semiconductor layer 140 are combined in the light emitting layer 130, thus the light-emitting layer emits light. However, since the holes provided by the P-type semiconductor layer 140 mostly inject into a portion of the light emitting layer 130 exactly under the electrode 142, the other portions of the light emitting layer 130 cannot emit light by insufficient carriers therein. Therefore, the intensity of the light provided by the light emitting diode 100 is not sufficient.
For solving the aforementioned problem, the area of the electrode 142 above the P-type semiconductor layer 140 is enlarged so that the electrons and holes may inject into mostly portions of the light emitting layer 130 and combine to each other. However, since the material of the electrode 142 is opaque, the light emitting area of the light emitting diode 100 would be decreased with enlarging area of the electrode 142. Accordingly, the emitting efficiency of the light emitting diode 100 cannot be enhanced by way of enlarging the area of the electrode 142.